Soil moisture sensor with built-in fault-detection capabilities

A soil moisture sensor (SMS) was built around a RISC-like microcontroller and common peripherals to perform data acquisition, signal processing, configuration, fault-detection and data communication with control/management systems. The SMS employs capacitance and heat-pulse techniques to determine the soil water content. The sensor uses the capacitance technique as the main method while the heat-pulse readings, acquired at a lower rate, are used for calibration and fault detection purposes. The temperature sensors and the heater were assembled in a four-needle probe. Several experiments were conducted for different types of soil. The results showed that this sensor could be applied in an effective way to measure the soil water content. Several tests are being performed to conclude about the sensor dependence with soil temperature and chemical composition as well about its long-term stability